The present invention relates to homing missiles, and more particularly, to a turnaway and dudding deterrent to an accidental attack by a weapon on its launching vessel.
In homing weapons, a search and acquisition system examines the surrounding environment, usually by acoustic or electronic means, for noise emanating from or, for other signs indicative of, the presence of a target. When first launched, the immediate proximity of the launching vehicle and the amplitude of its attendant noise shadow the presence of the target and increase the risk that the weapon's search system will acquire and return to the launching vehicle. Consequently, the weapon's search and acquisition system can not be activated until the weapon has traveled a predetermined distance (i.e., cleared the activation zone) from the launching vehicle.
Variable propagation conditions, quieting trends in vessel construction as well as mere quiescence, however, frequently mask the presence of a target until it is at close quarters with the launching vessel, often inside or just outside the activation zone. In these situations, as the azimuth, depth and range of the target is seldom immediately ascertainable, a vessel-to-vessel weapon must be capable of, on sudden launching, searching for and acquiring a vagariously moveable target at close quarters without endangering the launching vessel. Prior art weapon safety systems protect the launching vessel from an undesired attack by its own weapon by controlling activation and operation of the weapon's search and acquisition system. The weapon's system is not activated until the weapon has cleared a volume surrounding the launching vessel that can be best described as a spheroid having a semiaxis approximately colinear with the major axis of the launching vessel (i.e., a protective zone). If the weapon re-enters the spheroid, its system is deactivated. When the weapon is outside of the spheroid, its system is limited in its search to a lunular segment of a sphere. When launched against a target at close quarters with the launching vessel, a weapon having a prior art safety system has little or no opportunity for search and acquisition of the target.